Vehicles today, in particular terrain-going vehicles, are often driven on uneven ground and may impact impediments of various types. In order to deal with such irregularities and impediments while maintaining comfort and without the vehicle tipping over, it is important that sufficient contact between the wheels of the vehicle and the ground is ensured. Vehicles are, therefore, often designed with wheel bogies that cause the wheels to follow irregularities of the ground. A wheel bogie is a supplementary chassis that can be rotated relative to the principal chassis or frame of the vehicle. A wheel bogie normally has four wheels, which by means of wheel-supporting pendulum arms spread the load of the vehicle onto a greater number of axles and reduce the axle pressure, increase the load-bearing capacity, and improve the vehicle's handling when taking curves. A wheel bogie allows rotation around an axis that is parallel to the longitudinal direction of the vehicle and, in particular in the case of terrain-going vehicles, in combination with the ability to rotate around an axis that is perpendicular to the longitudinal direction of the vehicle. The pendulum arms may, as one alternative, be individually mounted to rotate, i.e. jointed at bearings at one of the ends, or they may be of a rigid, centrally mounted type consisting of a pendulum arm, such as, for example, a pendulum shaft designed to be rotated around a rotary bearing located at the centre of the pendulum shaft.
Terrain-going vehicles, such as forestry machines, comprise a crane with a crane arm that can be extended far from the vehicle and at the free end of which a tool, such a gripper or a harvester, can be attached. The crane and its load, which is located at the farthest extent of the arm, constitute a significant part of the vehicle and influence the position of its centre of gravity when the crane arm is extended from the vehicle. This leads to a torque that influences the vehicle in different directions, depending on the rotational position of the crane in the horizontal plane and its extension from the vehicle. Thus, if the crane is directed forwards, a torque is created in the forwards direction, while if the crane has been turned to one side a torque is created towards the side. In order to prevent the vehicle tipping over as a consequence of the torque that has arisen, the said torque must be counteracted and balanced, which takes place by means of a stabilisation arrangement. Such a stabilisation arrangement is particularly important when the vehicle is an articulated vehicle. An articulated vehicle comprises two chassis parts that are united with each other in a jointed manner, a forward frame and a rear frame that can be rotated by being set at an angle through a jointed waist, which makes the vehicle flexible and easy to maneuver. One disadvantage of articulated vehicles, however, is that such a vehicle is less stable when it is driven around a curve, since the centre of gravity of the vehicle is at the same time displaced.
One disadvantage of prior art stabilisation arrangements is that they are designed to be used principally when the vehicle is stationary. A further disadvantage of prior art stabilisation arrangements is that they are based on static calculations based on a series of parameters that have been determined in advance, for example based on the rotational position of the crane in the horizontal plane. Since the displacement of the centre of gravity of a vehicle is influenced by forces and torques that are not only static but also dynamic, the counteracting forces that are calculated in order to balance the vehicle will not always correspond to the actual or true torque that arises at the vehicle due to the displacement of the centre of gravity that occurs. The latter is particularly troublesome when the vehicle is in motion and subject to dynamic and more or less unpredictable forces and torques that do not necessarily depend on the rotational position of the crane.
Document SE 532683 describes a system for the stabilisation of a vehicle comprising actuators that generate a support force on a pendulum shaft in order to counteract rotation and imbalance of the vehicle that arise during rotation of the crane of the vehicle. The support force that is required to counteract the rotation is determined based on calculations based on the rotational position of the crane in the horizontal plane. Document WO2013178886 describes a system to stabilise a forestry machine where the torque that acts on a part of the chassis is determined, after which the magnitude and direction of a counteracting torque are determined.
Despite the prior art solutions within the technical area, there is a requirement to achieve a system for the stabilisation of vehicles that is effective and safe, that can be applied when the vehicle is being driven, and that minimises the risk of the vehicle tipping over.